Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$246.67	9.255%	$269.4993	$269.50	$269.50	$269.50
Purchase #2	$57.51	11.215%	$63.9597	$63.96	$63.95	$64.00
Purchase #3	$173.45	4.424%	$181.1234	$181.12	$181.10	$181.10
Purchase #4	$53.92	10.513%	$59.5886	$59.59	$59.60	$59.60
Purchase #5	$77.74	11.387%	$86.5923	$86.59	$86.60	$86.60
Purchase #6	$207.89	13.282%	$235.5019	$235.50	$235.50	$235.50
Purchase #7	$93.53	6.114%	$99.2484	$99.25	$99.25	$99.20
7 purchase totals =	$910.71		$995.5136	$995.51	$995.50	$995.50